Processes are known for forming a metal composition containing degenerate dendritic primary solid particles homogeneously suspended in a secondary phase having a lower melting point than the primary solids and having a different metal composition than the primary solids. In such thixotropic alloys, both the secondary phase and the solid particles are derived from the same alloy composition. In such processes, the metal alloy is heated to a point above the liquidus temperature of the metal alloy. The liquid metal alloy is thereafter passed into an agitation zone and cooling zone. The liquid alloy is vigorously agitated as it is cooled to solidify a portion of the metal alloy to prevent the formation of the interconnected dendritic networks in the metal and form primary solids comprising discrete, degenerate dendrites or nodules. Surrounding the degenerate dendrites or nodules, is the remaining unsolidified liquid alloy. This liquid-solid metal alloy composition is then removed from the agitation zone. Such mixtures of liquids and solids are commonly referred to as thixotropic alloys. An example of the above described process is shown in U.S. Pat. No. 3,902,544, issued Sept. 2, 1975, to M. C. Flemings, et al.
U.S. Pat. No. 3,936,298 issued Feb. 3, 1976, to Robert Mehrabian, et al. describes a thixotropic metal composition and methods for preparing this liquid-solid alloy metal composition and methods for casting the metal compositions. This patent describes a composite composition having a third component. These compositions are formed by heating a metallic alloy to a temperature at which most or all of the metallic composition is in a liquid state and feeding the liquid metal into a cooling zone where the metal is cooled while being vigorously agitated to convert any solid particles therein to degenerate dendrites or nodules having a generally spheroidal shape. The agitation can be initiated either while the metallic composition is all liquid or when a small portion of the metal is solid, but containing less solid than that which promotes the formation of a solid dendritic network.
The types of thixotropic metals produced in the herein described invention have been described in U.S. Pat. No. 3,902,544 and U.S. Pat. No. 3,936,298. These descriptions of thixotropic-type alloys, as contained in those patents, are herein incorporated by reference. However, the method of making the alloy in the herein described invention is quite different from that described in the two above-mentioned patents.